A mining plan usually is established prior to mining a resource, such as iron ore or any other ore. A number of samples may be taken from drill holes and a property of the samples, such as an iron grade, is analysed. Statistical methods are then used to predict the property at locations in the proximity of the drill holes.
Kriging is an established statistical method that is used for this purpose. However, kriging has significant disadvantages. For example, kriging systematically over- or underestimates values (“conditional bias”).